Thursday, July 23, 2009

Single Atom Substitution in Water Purfication Process Gives Purified Water Long Shelf Life

By substituting a single atom in a molecule widely used to purify water, researchers at Sandia National Laboratories have created a far more effective decontaminant with a shelf life superior to products currently on the market.

The water-treatment reagent, known as a coagulant, is made by substituting an atom of gallium in the center of an aluminum oxide cluster — itself a commonly used coagulant in water purification, says Nyman.

The substitution isn’t performed atom by atom using nanoscopic tweezers but rather uses a simple chemical process of dissolving aluminum salts in water, gallium salts into a sodium hydroxide solution and then slowly adding the sodium hydroxide solution to the aluminum solution while heating.

“The substitution of a single gallium atom in that compound makes a big difference,” said Nyman. “It greatly improves the stability and effectiveness of the reagent. We’ve done side-by-side tests with a variety of commercially available products. For almost every case, ours performs best under a wide range of conditions.”

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The Sandia coagulant attracts and binds contaminants so well because it maintains its electrostatic charge more reliably than conventional coagulants made without gallium, itself a harmless addition.

The new material also resists converting to larger, less-reactive aggregates before it is used. This means it maintains a longer shelf life, avoiding the problem faced by related commercially available products that aggregate over time.

“The chemical substitution [of a gallium atom for an aluminum atom] has been studied by Sandia’s collaborators at the University of California at Davis, but nobody has ever put this knowledge to use in an application such as removing water contaminants like microorganisms,” said Nyman.